<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border: 1px solid red;
      /*margin-top:  100px;*/
      /*margin-left: 50px;*/
      /*margin-bottom: 100px;*/
      margin: 100px;
      margin: 100px 200px;
      margin: 100px 200px 300px 400px;
      /*居中写法*/
      margin: 100px auto
    }
    #d2{
      width: 100px;
      height: 100px;
      border: 1px solid blue;
      margin-top: 50px;
    }
    /*行内元素上下外边距无效*/
    #s1{
      margin-right: 50px;
      margin-top: 100px;
    }
    /*左右相邻彼此添加外边距，两者相加*/
    #s2{
      margin-left: 50px;
    }
    #big{
      width: 200px;
      height: 200px;
      background-color: green;
      overflow: hidden;
    }
    #big>div{
      width: 50px;
      height: 50px;
      background-color: purple;
      margin-top: 50px;
      margin-left: 50px;
    }
  </style>
</head>
<body>
<div id="big"><div></div></div>

<span id="s1">span1</span>
<span id="s2">span1</span>
<div id="d1"></div>
<div id="d2"></div>
</body>
</html>